The present invention relates to sealed double glazing units and, more particularly, to such a unit comprising an outer pane and an inner pane which are spaced apart by a perimeter seal.
It is known to construct glass wall assemblies in which adjacent glass sheets are secured together and are secured to structural members of a building by means of metal plates to which the sheets are bolted.
It is desirable, for their insulative properties, to construct glass wall assemblies from double glazing units. But when seeking to provide the desired outward appearance of such units, in which the outer glass sheets appear to the observer to be mounted edge-to-edge to form an uninterrupted glass wall, problems arise in mounting the units without a frame enclosing the edges of each double glazing unit. Such units can be mounted either using adhesives or mechanical fixings for fixing the units to structural supporting members of a building. Mechanical fixing is preferred for greater mechanical security, but there are difficulties in securing a double glazing unit mechanically without enclosing the edges, while ensuring that the seal of the double glazing unit is maintained to prevent ingress of moisture and air into the evacuated space between the panes of the unit.
In U.S. Pat. No. 4,581,868 there is described a construction in which sealed double glazing units are secured to supporting members, with the outer sheets of the units sealed edge-to-edge by a sealing compound, and each of the units secured to the supporting members by mechanical fixings which pass through flanges of the outer sheets outside the seals of the unit.
U.S. Pat. No. 4,680,206 provides another solution to the problem of the mechanical fixing of a sealed double glazing unit to supporting members. According to this patent, a mechanical fixing means passes through the sealed air space of the double glazing unit, with a moisture-tight seal being provided between the panes and the mechanical fixing, in such a manner as to permit the double glazing unit to flex under the variable loads which are encountered in service, such as wind load. According to the patent, the sealed double glazing unit comprises an outer pane and an inner pane which are spaced apart by a perimeter seal, and has at least one fixing position within the perimeter seal for fixing the unit without obstructing its outer edge. At the fixing position there is a fixing assembly which is attached to one of the panes in a manner which permits the unit to flex under wind load without impairing the seal of the unit. The fixing assembly, among other things, acts as a sleeve to protect the panes from contact with the fixing member or bolt which is used to secure the unit to the fixing member. As illustrated in FIG. 4 thereof, a spacer in the form of a torus has the opposing end faces thereof secured by an inner silicone seal and an outer butyl seal to the opposing faces of the panes, thus presumably preventing a loss of integrity in the area of the fixing assembly from impairing the integrity of the remainder of the unit.
Even when such a spacer is provided about the fixing assembly, the fixing assembly requires within and between the panes numerous elements including a resilient bush, a fiber washer, a clamping disc, a metal washer, a clamping nut, and a distance-maintaining piece. The cost of such materials, and the labor required to apply them, add substantially to the cost of the unit. Apart from these economic factors, the mechanical clamping of the fixing assembly about one or both panes can lead to breakage of the pane being clamped or the introduction of internal stresses within the pane rendering the same more subject to breakage in use. Furthermore, the presumably air-tight connection between the spacer and the panes is effected by a thin layer of sealant which may not provide adequate protection against leakage from the fixing assembly within the spacer into the remainder of the unit outside the spacer.
Accordingly, it is an object of the present invention to provide an improved sealed double glazing unit which does not have a fixing assembly mechanically attached to either pane.
Another object is to provide such a unit afforded improved air-tight isolation of the fixing assembly from the remainder of the unit.
A further object is to provide such a unit in which the fixing assembly is secured in place without being mechanically attached to either pane.
It is also an object of the present invention to provide such a unit having a simplified and more economical construction.
It is a further object to provide a simple, fast and economical method of making such a unit.